This invention relates to an improved package for containing, serving and cooking particulate food stuffs such as popcorn in a microwave oven, and for an improved method of making such packages.
It is commonly known that early attempts to produce paper containers for cooking particular foods in microwave ovens such as illustrated in U.S. Pat. No. 3,973,045 issued to Brandberg, et al., involved a compact gussetted bag made from multiplys of paper and incorporated a flexible body which is expanded to accommodate the increased volume of popped popcorn. However, while the Brandberg container functions desirably for its intended purpose, it still leaves up to twenty-five percent (25%) of the corn kernels unpopped and five percent (5%) burned after exposure for approximately two and one-half minutes of microwave cooking time. Accordingly, attempts have been made throughout the years to remedy these deficiencies.
In recent years, patents to Teich, et al., U.S. Pat. No. 4,156,806, and to Ishino, et al., U.S. Pat. No. 4,335,291, disclose methods for improving the efficiency of popcorn containers which rely primarily on concentrating microwave energy at the base of a conically shaped bowl where corn kernels were clumped for the purpose of improving the efficiency and speed of popping. One important embodiment of that technology as disclosed by Teich used a microwave lossy powder of particulate material in the base area. The lossy material heated up and radiated that generated heat to the kernels located closest to it, thereby adding to the heat induced in the corn kernels by direct impingement of the microwave energy on the same.
Later, however, it was taught by Bohrer, et al. in U.S. Pat. No. 4,553,010, that the popcorn would pop more rapidly and more efficiently by avoiding the clumping of corn kernels in one area of a popping container and designing for the packaging of said kernels to rest in uniform proximity to the lossy material and being spaced no more than an average kernel's diameter away from the said lossy material. To accomplish such a feat, the lossy material was applied as a layer at the bottom of a flat container and the kernels generally evenly distributed in an unclumped fashion along said bottom of the microwaveable package or container. The bottom coating of such containers were in the form of a coated panel placed into the package.
It has been found that the prior applications and designs of the metallized lossy microwave assist materials have intrinsically required the use of lubricants such as greases, oils, or butter, which have proven to have an insulating character deterrent to the creation of heat in the microwave ovens during usage. A means for applying metallized lossy material which would not require said lubricants would be a substantial advancement in the art.
More importantly, the placement of a lossy coated panel in the bottom of gussetted bags, although not described in detail in the prior art, has proven to be extremely difficult and expensive to manufacture. Additionally, the requirement of uniformly scattering popcorn kernels at the bottom of the bag is cumbersome and time-consuming, and difficult to sustain. Also, coated panels are difficult to regulate precisely in their functioning, and it is difficult to determine precisely the type of metallic powder or flakes which are needed to retain the heat generated by the microwave cooking process.
Finally, it is of necessity during ordinary filling operations that particulate food stuffs such as popcorn will ordinarily be clumped together and particularly when oils or greases are applied therewith, and a means for developing a heat-assist which compensates for such clumping during filling without any detrimental effects, while at the same time creating the efficiencies of cooking from a heat-assist to the kernels which are unclumped without the awkward manufacture of a bottom coated panel is a substantial advancement in the art.
Other art known to applicants which include the metallization of a liner material, such as paper, or polymer, are shown in U.S. patents to Beckett, U.S. Pat. No. 4,398,994, U.S. Pat. No. 4,517,045, and U.S. Pat. No. 4,552,614. U.S. Pat. No. 3,647,508, shows the concept of patterned application of metal onto films, such as plastic film. In addition, metal application to a film is shown in the U.S. Pat. No. 4,242,378, U.S. Pat. No. 4,532,002, U.S. Pat. No. 4,448,636, U.S. Pat. No. 3,935,334, U.S. Pat. No. 3,985,597, U.S. Pat. No. 2,748,031, and U.S. Pat. No. 2,139,640. In addition, Canadian patent No. 1,153,069 discloses a food receptacle for microwave cooking, that includes a conductive elemental metal incorporated into such a receptacle to enhance microwave cooking, or at least to achieve some surface browning of the heated food product. See also U.S. Pat. No. 3,671,270; U.S. Pat. No. 3,853,280; U.S. Pat. No. 4,267,420; U.S. Pat. No. 4,450,180; U.S. Pat. No. 3,993,045; U.S. Pat. No. 4,219,573; U.S. Pat. No. 4,038,425; and, U.S. Pat. No. 4,292,332.